• ReleaseNotes

Release Notes for HMI Vector Magnetic Field Data for AR 11158

This page describes the data files being released for AR 11158 and provides information about how to use them. For more information about the way the data have been computed and the uncertainties in them, please refer to VectorPaper.

Data include complete 5-day time series of 12-minute cadence vector magnetic field and associated quantities.

• Data are provided as CCD cut-outs and as remapped and projected values.
• There are also one-per-day samples in the same formats.
• Movies show summaries of the vector data and provide context.

• Please make use of this [http://hmi.stanford.edu/doc/magnetic/guide.pdf Practical Guide] for reading HMI Vector Magnetograms and interpreting geometry information

Vector Field Cut-outs

• A ~900 MB tar file is provided for each of the 5 days from February 12 - 16, 2011.
• Each tar file contains 120 sets of 11 FITS files (1320 files), one set for each 12-minute interval of the day.
• Also included are 5 summary files listing the contents of the directory and giving information about the processing of the data series
  • index.html, index.json, index.txt, JSOC_20111103_001_IN.drmsrun and JSOC_20111103_001_IN.qsub.
• The names of the FITS files indicate the data series, time, and quantity in the file. Each is 650 * 600 pixels. Pixels that are not inverted are NANs. The files are RICE compressed. Each file contains keywords that provide geometry and other necessary information (described below).
• An example of a file name is
  • hmi_test.B_720s_cutout.1984.20110212_000000_TAI.azimuth.fits
• where hmi_test.B_720s_cutout is the series name, 1984 is the region number, 20110212_000000_TAI is the center time of the observation, and azimuth is the component in that map.
• The three field components are:

  • field is the total average field strength for the pixel.

  • inclination is the angle of the field vector relative to the line of sight

  • azimuth is angle of the field vector relative to 'up' on the CCD, i.e. nearly solar south a disk center.

• The computed uncertainties of the individual components are given in

  • field_err, azimuth_err, and inclination_err

• The square root of the four covariances are given in combined names

  • field_az_err, field_inclination_err, field_az_err, and inclin_azimuth_err

• Maps of Quality and Confidence are given in confid_map and qual_map

  • qual_map contains 32-bit integers providing encoded information for each pixel about the Stokes vector computation (bist 28-31), inversion results (bits 24-27), and disambiguation (bits 0-7). Details are provided at [http://hmi.stanford.edu/doc/magnetic/qualmap_description.pdf Qual_Map]

  • confid_map contains and integer that provides a linear estimation of the confidence in the final result at the pixel. A lower number is better than a higher number.

• Keywords in each FITS file provide information about the data.

  • Specific Keywords: [http://hmi.stanford.edu/doc/magnetic/hmi.B_720s.KeywordsSegments.pdf HMI_B Keywords]

  • General JSOC Keywords: [http://jsoc.stanford.edu/doc/keywords/JSOC_Keywords_for_metadata.pdf JSOC Keywords]

  • WCS Coordinates: [http://sun.stanford.edu/~beck/JSOC/HMI_WCS_Dummies.pdf WCS Keywords]

Projected and Remapped Vector Magnetic Field

Sample Data

Summary and Context Movies

• Br Cutout Movie

  • The Br Cutout Movie shows the polarity of the radial field in black (inward) and white (outward). The color table saturates and a contour is drawn at the 600 G level. The cut-outs are in native CCD coordinates on a fixed 600 by 600 grid. The center pixel is the one nearest a point tracked at the Carrington rate, but of course some jitter remains. The HMI CCD is rotated such that solar north points very nearly to the bottom of the frame. Toward the end of the movie a dark region appears at the edge of the frames where data were not inverted. Each frame is labeled with the UT time. Note the 20s offset due to the use of TAI time in the original data series.

• Vector Field Movie

  • The Vector Field Movie shows the radial field in black (negative) and white (positive) with a contour at 600 G. The transverse component is shown by small vectors whose length is related to strength and whose color depends on the radial field direction (blue = positive, red = negative). Vectors are shown only when the transverse field is greater than 200 G. These data have been remapped and interpolated at high resolution onto a cylindrical equal area Lambert projection centered at a fixed point at the center of the region that is tracked at the Carrington rate. The vector field components have been transformed to Br, Btheta and Bphi. The UT time is shown for each frame.

• Hedgehog

  • There are three hedgehog versions of the field movie. In each red and blue indicate the direction and strength of the radial component of the field. At each grid point a small line shows the direction of the field originating on the surface. The length of the line corresponds to the total field strength. Vectors are shown only for points with total field strength greater than 200 G. The glyph on the lower right shows the orientation and projection of the movie relative to the a standard disk and indicates time of day with the small point in the outer circle. TAI time is indiated at the top of each frame. The movies show the full region at two scales and focus in on the east and west part of the region as it evolves.

• Intensity and Blos

  • The side-by-side frames show the continuum intensity (corrected for limb darkening) in shades of yellow, oragne, and black on the left and the line-of-sight component of the magnetic field in black and white on the right. These are cut outs of the field rotated to place north at the top of the frame. The tracking is at the Carrington rate and some jitter remains due to rounding. The time of each frame is indicated.

• Tracked Patches

  • Two movies show the full disk magnetic field evolution during the first and second halves of the month of February. The colored regions are HMI Active Region Patches (HARPs) identified and tracked automatically from one image to the next. Each HARP is assigned a number (shown on the right) and color coded for ease of identification. Active pixels above a threshold are shown in black and the pixels inside the colored blobs show the instantaneous HARP boundary. The rectangular box around each region encloses the blob. The gray areas suggest how the region is changing in time. The northern and southern HARP numbers are indicated at the top and bottom right. Regions with a + in the center are numbered NOAA active regions and the NOAA numbers are shown on the right, near the HARP numbers. The + shows the NOAA-provided location and the NOAA numbers are organized from from left to right in the appropriate hemisphere. AR 11158 is the orange region labeled as HARP 883 in the southern hemisphere that crosses central meridian on February 14.

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